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core/dracut/ignition-ostree: add a bwrap-in-sysroot helper
This introduces a new `coreos-sysroot-bwrap` helper in initramfs, for binaries that need to be executed with the final sysroot as a target, but before the pivot-root happens.
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overlay.d/05core/usr/lib/dracut/modules.d/40ignition-ostree/coreos-sysroot-bwrap
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#!/usr/bin/env bash | ||
# | ||
# Needed to work around the initrd `rootfs` / filesystem not being a valid | ||
# mount to pivot out of. For reference, see: | ||
# - https://github.com/torvalds/linux/blob/26bc672134241a080a83b2ab9aa8abede8d30e1c/fs/namespace.c#L3605 | ||
# - https://gist.github.com/jlebon/fb6e7c6dcc3ce17d3e2a86f5938ec033 | ||
set -euo pipefail | ||
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TMP_CHROOT_DIR="" | ||
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main() { | ||
setup_chroot_tmpdir | ||
run_chrooted_bwrap "$@" | ||
} | ||
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setup_chroot_tmpdir() { | ||
TMP_CHROOT_DIR=$(mktemp --directory --tmpdir=/mnt '.coreos-sysroot-bwrap.tmp.XXXXXXXXXX') | ||
mount --bind / "${TMP_CHROOT_DIR}" | ||
mount --make-private "${TMP_CHROOT_DIR}" | ||
mount --bind "${TMP_CHROOT_DIR}" "${TMP_CHROOT_DIR}" | ||
for mnt in proc sys dev; do | ||
mount --bind /$mnt "${TMP_CHROOT_DIR}"/$mnt | ||
done | ||
touch "${TMP_CHROOT_DIR}"/run/ostree-booted | ||
mount --bind /sysroot "${TMP_CHROOT_DIR}"/sysroot | ||
} | ||
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run_chrooted_bwrap() { | ||
chroot "${TMP_CHROOT_DIR}" \ | ||
/usr/bin/env --chdir /sysroot \ | ||
bwrap \ | ||
--unshare-pid --unshare-uts --unshare-ipc --unshare-net \ | ||
--unshare-cgroup-try --dev /dev --proc /proc --chdir / \ | ||
--ro-bind usr /usr --bind etc /etc --dir /tmp --tmpfs /var/tmp \ | ||
--tmpfs /run --ro-bind /run/ostree-booted /run/ostree-booted \ | ||
--symlink usr/lib /lib \ | ||
--symlink usr/lib64 /lib64 \ | ||
--symlink usr/bin /bin \ | ||
--symlink usr/sbin /sbin -- "$@" | ||
} | ||
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cleanup() { | ||
if test -z "${TMP_CHROOT_DIR}"; then | ||
return | ||
fi | ||
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umount --lazy --recursive "${TMP_CHROOT_DIR}" | ||
umount --recursive "${TMP_CHROOT_DIR}" | ||
rmdir "${TMP_CHROOT_DIR}" | ||
} | ||
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trap cleanup EXIT | ||
main "$@" |
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